It is known to control the substantially automatic operation of a rotary evaporator by means of a processor in such a manner that the distillation process proceeds in a substantially automatized sequence. A main component of a rotary evaporator is a rotary flask adapted to be rotated about its longitudinal axis by a motor operatively connected in most cases to a neck portion of the flask. The sample to be distilled is filled into the rotary flask. In a known system the flask floats in a temperature-controlled heating bath.
The flask is connected to a condenser and a distillate collector receptacle in a closed vacuum system. Heating of the rotary piston in the heating bath causes the sample solution to be concentrated by evaporation. The vapors are condensed in the condenser and collected in the distillate collector receptacle. For enabling a sample to be automatically evaporated to a desired concentration and a desired amount, the rotary flask of an already known processor-controlled rotary evaporator is additionally mounted for pivotal movement about an axis adjacent its neck, thereby enabling it to be immersed in the heating bath to a varying depth, depending on the sample volume. The angle to which the flask is pivoted relative to a predetermined axis may be detected by means of a sensor, for instance a potentiometer. The potentiometer signal varies in response to the filling amount, so that in principle it is possible in this manner to meter or to determine the amount of the sample filled into the flask by determining its pivot angle. It is thus possible to determine the time at which for instance a solution has been evaporated to a desired concentration to which the processor has been pre-set, whereupon the apparatus may be automatically switched off.
This system is disadvantageous in the first place, in that the pivotal mounting of the rotary flask permitting it to be immersed into the heating bath to a varying depth requires the employ of a flexible seal which has to be vacuum-tight. In addition, different sample solutions having different specific weights require different calibrations of the apparatus, because a given amount of a solution having a higher specific weight results in a greater immersion depth of the flask, and thus in a greater pivot angle as measured by the sensor, than the same amount of a solution having a lower specific weight. This metering system for automatically filling the rotary flask is thus highly complicated and cumbersome.
A further, disadvantage of the known rotary evaporator results from the fact that its operation has to be interrupted for emptying the distillate collector receptacle. As the entire system operates under vacuum, the distillate collected in the distillate collector receptacle of the known rotary evaporator can only be drained therefrom after the vacuum system has been vented. The resulting downtimes during which the apparatus is out of operation are particularly annoying when greater amounts of a sample solutions are to be distilled.